Estrogen predicts breast cancer recurrence: study

By Julie Steenhuysen

CHICAGO (Reuters) - Blood taken from women whose breast cancer returned showed high levels of estrogen even though many had been treated with estrogen-blocking drugs, U.S. researchers said on Thursday.

They said the finding suggests women who have had breast cancer should take extra steps -- such as regular exercise and weight management -- to reduce their estrogen levels and minimize the risk that their cancer will return.

Estrogen is strongly linked with the initial development of many breast cancers, but few studies have looked at the link between high estrogen levels and cancer recurrence, especially in women who are taking anti-estrogen drugs like tamoxifen.

"This is the largest study to date and the only one to have included women taking agents such as tamoxifen to reduce estrogen's effect on cancer growth," said Cheryl Rock, a professor of preventive medicine at the University of California, San Diego, whose study appears in the journal Cancer Epidemiology, Biomarkers and Prevention.

Rock said taking anti-estrogen drugs like tamoxifen may not completely wipe out the hormone's effect in women who have high levels of estrogen. Tamoxifen transformed breast cancer therapy when it was shown to reduce the risk of cancer coming back by close to 50 percent.

But Rock said women on that pill or a newer class of drugs called aromatase inhibitors should also consider some basic preventive measures.

"You can't just assume because you've got one drug that has good effect that you should forget about all of the other useful things that you might be able to do," she said in a telephone interview.

Rock and colleagues drew their conclusions from a dietary intervention trial that followed 3,088 women who had been treated for early stage breast cancer but who were cancer-free at the time they enrolled.